Field of the Disclosure
The present disclosure relates to additive manufacturing and more particularly, to multiple beam additive manufacturing.
Background Art Discussion
Additive manufacturing (also known as three-dimensional printing) techniques have been used to manufacture three-dimensional structures of almost any shape. Using an additive process, successive layers of material are deposited to form the structure based on data defining a 3D model of the structure. In some methods, the successive layers forming the structure are produced by depositing successive layers of powder material and using a light beam (e.g., laser light) to bind or fuse the powder material in selected regions of each layer. Examples of these methods include selective laser sintering (SLS) wherein the laser sinters the powder particles in the selected regions to form each build layer of the structure and selective laser melting (SLM) wherein the laser melts the powder in the selected regions such that the melted material hardens to form each build layer of the structure.
Although such laser additive manufacturing (LAM) techniques have been successful, the movement of the laser to the selected regions often slows the build rate and the speed of manufacturing. Multiple beams have been used in an effort to increase speeds, but scanning multiple beams across the powder layers may result in stresses being created in the fused material of each build layer. The thermal energy, for example, may cause thermal part stress, which may deform the three-dimensional structure as the build layers are formed. As such, LAM techniques have not been as successful when used with certain materials such as superalloys because thermal stresses may result in cracking. Also, LAM techniques have not been as successful when used with powder material having larger particle sizes because the power of the laser may not be sufficient to melt and fuse larger particles sizes without causing excessive thermal stress.
Moreover, faster build rates generally require energy to be introduced into the powder bed faster (i.e., at higher power). Increasing the power of a LAM system is challenging because optical elements must be larger and cooling must be increased to withstand the higher power. The scanning mirror in such systems becomes less responsive with the increased size, which decreases the scanning speed and reduces build speed. Attempts at using multiple beams in SLM systems have been unsuccessful because of the challenges involved with scanning the same area with multiple beams.
Accordingly, there is a need for an additive manufacturing system and method that allows faster build rates while reducing thermal stresses in the fused material.